I’d like to dedicate this book to three people. My brother Bob inspired me to become an engineer. I recall one time when he was home from college and presented me with the N-body problem [Wiki01] and the four color map problem [Wiki02]. My high school science teacher, Mr. Sanderson, spurred me on to explore topics such as why there is air. My mechanical engineering professor at Duke, Dr. George Pearsall, encouraged exploration. In his strength of materials class, I discovered why my guitar strings broke. To each of them, I give thanks.